1. Technical Field
The present invention relates to a liquid developer transport device that separates a liquid carrier from a liquid developer, and an image forming apparatus such as a facsimile, printer, and copier including the liquid developer transport device.
2. Related Art
A wet-process image forming apparatus using a high-viscosity liquid developer in which toner particles of solid components are dispersed in a liquid carrier to develop an electrostatic latent image for visualizing the electrostatic latent image has been proposed. The developer used in the wet-process image forming apparatus contains a liquid carrier of an electrically insulating organic solvent such as silicone oil, mineral oil, vegetable oil, and toner particles of solid components dispersed in the liquid carrier. The particle diameter of the toner particles is about 1 μm. On the other hand, the particle diameter of powder toner particles used in a dry-process image forming apparatus is about 7 μm. Accordingly, the image quality of an image formed by the wet-process image forming apparatus is higher than the image quality of an image formed by the dry-process image forming apparatus.
The liquid carrier of the developer used in the wet-process image forming apparatus prevents flying of the toner particles having a particle diameter of about 1 μm and facilitates the movement of the toner particles by the action of an electric field in the developing and transfer steps. Accordingly, the liquid carrier is a necessary component for preservation of the liquid developer, transportation of the liquid developer, the developing step, and the transfer step. However, the liquid carrier also attaches to non-image areas, and the excessive liquid carrier after development may cause disadvantageous phenomena for image formation such as transfer irregularities. On this account, the liquid carrier of the liquid developer on a photoconductor and a transfer member is removed (squeezed) and collected. Further, also the liquid developer remaining on the photoconductor and the transfer member after the transfer step is removed and collected.
For reuse of the collected liquid developer, an image forming apparatus of allowing the liquid developer removed and collected by cleaning means to pass through filtering means including a foam on which an electric field acts for separating and extracting the liquid carrier from the liquid developer has been considered (for example, see JP-A-2000-89578). FIG. 1 shows an embodiment of a monochrome image forming apparatus in the related art. A liquid developer stored within a liquid developer container 31 is fed to a stirring tank 53. When the toner particle concentration of the liquid developer stored within the liquid developer container 31 becomes low, the high-concentration liquid developer is fed from a supplementary liquid developer tank 54 to the stirring tank 53 by a pump 553, and further, a liquid carrier is fed from a liquid carrier tank 57 to the stirring tank 53 for adjustment of the toner particle concentration in the liquid image developer stored in the stirring tank 53 to a constant value. When the toner particle concentration of the liquid developer becomes high, the liquid carrier is fed from the liquid carrier tank 57 to the stirring tank 53. The liquid developer with adjusted constant toner particle concentration is fed to the liquid developer container 31 by a pump 551. The liquid developer collected by a photoconductor cleaning device including a cleaning blade 17 and a liquid developer collecting part 18 is stored in a photoconductor buffer tank 51, and then, fed to a filtering unit 56. The liquid developer collected by an intermediate transfer member cleaning device including a cleaning blade 46 and a liquid developer collecting part 47 is also fed to the filtering unit 56. The liquid carrier is separated from the liquid developer filtered in the filtering unit 56, and the liquid carrier is stored in the liquid carrier tank 57 and reused.
FIG. 2 shows an embodiment of a color image forming apparatus in the related art. Developers stored within liquid developer containers 31Y, M, C, K are fed to stirring tanks 53Y, 53M, 53C, 53K. When the toner particle concentrations of the liquid developers stored within the liquid developer containers 31Y, M, C, K become low, the high-concentration liquid developers are fed from supplementary liquid developer tanks 54Y, 54M, 54C, 54K to the stirring tanks 53Y, 53M, 53C, 53K by pumps 553Y, 553M, 553C, 553K, and further, a liquid carrier is fed from a liquid carrier tank 57 to the stirring tanks 53Y, 53M, 53C, 53K for adjustment of the toner particle concentrations in the liquid image developers stored in the stirring tanks 53Y, 53M, 53C, 53K to constant values. When the toner particle concentrations of the liquid developers become high, the liquid carrier is fed from the liquid carrier tank 57 to the stirring tanks 53Y, 53M, 53C, 53K. The liquid developers with adjusted constant toner particle concentrations are fed to the liquid developer containers 31Y, M, C, K by pumps 551Y, 551M, 551C, 551K. The liquid developers collected by photoconductor cleaning devices including cleaning blades 17Y, 17M, 17C, 17K and liquid developer collecting parts 18Y, 18M, 18C, 18K are stored in photoconductor buffer tanks 51Y, 51M, 51C, 51K, and then, fed to a filtering unit 56. The liquid developers collected by an intermediate transfer member cleaning device including a cleaning blade 46 and a liquid developer collecting part 47 are also fed to the filtering unit 56. The liquid carrier is separated from the liquid developers filtered in the filtering unit 56, and the liquid carrier is stored in the liquid carrier tank 57 and reused.
The image forming apparatuses in the related art have disadvantages that the solid components in the collected liquid developer remain in the foam incorporated in the filtering means and the performance of the filtering means quickly becomes lower.